 Hi and welcome to the session, I am Deepika here. Let's discuss the question. Find the principal value of cos inverse minus 1 over root 2. So let's start the solution. Now before finding the principal value of cos inverse minus 1 over root 2, just look at the table. This table shows the domains and ranges that is the principal value branch of inverse trigromatic function. So from this table we know that the range of the principal value branch of cos inverse is close interval 0 to pi. So this is the key idea behind this question. So let's start the solution equal to, which is equal to cos question. That is the principal value of cos e pi by 4. I hope the question is clear to you. Why not enjoy yourself.